Galvanizing, << GAL vuh nyz ihng, >> is the process of coating such metals as iron and steel with a thin protective layer of zinc or zinc alloy. This layer protects the metals from corrosion (chemical damage). The zinc helps prevent corrosion because it reacts with many chemicals more easily than iron does. For example, when iron reacts with oxygen, it forms iron oxide (rust). However, if the iron has been galvanized, the zinc protects the iron by reacting with the oxygen and forming zinc oxide before rust can form.
Steel is the most commonly galvanized metal. One simple and widely used method of applying a zinc coating to steel is called hot-dip galvanizing. This method involves dipping steel in a hot bath of liquid zinc. In some cases, steelmakers mix other metals, such as aluminum, antimony, cadmium, and tin, with the zinc. Manufacturers add such metals in order to improve the appearance or the protective qualities of the coating. Metal pails and similar small objects are dipped in the zinc bath and galvanized one at a time. Steelmakers galvanize huge sheets of steel by passing them continuously through the zinc bath and coiling them up afterward. This method of galvanizing forms coatings that are about 3/1,000 inch (0.076 millimeter) thick. Sheet steel galvanized in this way may later be stamped or pressed to form such items as automobile body panels and steel roofing and siding. See Iron and steel (Finishing) .
A less widely used method of galvanizing steel is called electrogalvanizing. This process involves placing steel in a solution of zinc sulfate and water. A flow of electricity causes the zinc in the solution to form a thin layer on the surface of the steel. Electrogalvanizing is used chiefly to galvanize a continuous piece of steel. See Electroplating .
